Machine and method for forming continuous tubes



Oct. 30, 1962 WAGNER ETAL 3,060,814

MACHINE AND METHOD FOR FORMING CONTINUOUS TUBES Filed Feb. 18, 1959 4 Sheets-Sheet l Oct. 30, 1962 E. E. WAGNER ETAL 3,060,814

MACHINE AND METHOD FOR FORMING CONTINUOUS TUBES Filed Feb. 18, 1959 4 Sheets-Sheet 2 Oct. 30, 1962 E. E.WAGNER ETAL MACHINE AND METHOD FOR FORMING CONTINUOUS TUBES 4 Sheets-Sheet 3 Filed Feb. 18, 1959 E. E. WAGNER ETAL 3,060,814

Oct. 30, 1962 MACHINE AND METHOD FOR FORMING CONTINUOUS TUBES 4 Sheets-Sheet 4 Filed Feb. 18, 1959 ulaln 3,360,814 MAC AND IVEIIHGD FUR FORMENG CONTINUOUS TUBES Edward E. Wagner, Chester, and Lloyd H. Gibson, Richmond, Va., assignors to Philip Morris Incorporated,

New York, N.Y., a corporation of Virginia Filed Feb. 18, 1959, Ser. No. 794,126 9 Claims. (Cl. 93-1) The present invention is concerned with a continuous tube forming machine and a method of forming such tubes. As disclosed herein the machine and method are particularly adapted to forming a supporting tube of paper or equivalent material around consecutive spaced elements comprising cylindrical stubs of filter paper adapted to be incorporated ultimately in filter type cigarettes having recessed ends. By transversely severing the tube at appropriate points short individual cylindrical filter elements are derived adapted to be incorporated in a cigarette each element having a section of filter material at one end and a hollow or recessed opposite end.

The filter sections are separated in the continuous tube by hollow spaces equal to the length of two of the recessed ends of the ultimate cigarette and in order that the tube, and the shorter sections thereof, will have sufiicient strength and firmness for subsequent handling the sheet material must have substantial strength and stiffness particularly at the hollow areas. In general such material must be considerably thicker and heavier than ordinary cigarette paper. The necessary use of such heavier and stifler paper, however, introduces difficulties of manufacture and maintenance of the desired circular shape. The common shaping and tube sealing means, such as is used in making cigarette rods, if employed for making tubes of the character and from the strip material here concerned results in a tube which is noncircular and particularly is fiatted, on the seam side. Also the seam is not dependable but has a distinct tendency to pop open before the adhesive becomes adequately set to constitute a permanent bond. The apparatus comprising the present invention and its manner of operation remedy these difficulties and result in a continuous tube which is uniformly circular in shape and adequately sealed and stifi and strong for the purpose.

In accordance with the principles of the invention the paper for the tube is pre-coated with a dried thermosetting adhesive, and a wet adhesive is applied at the longitudinal seam which is then folded down and the tube then proceeds into tube sealing and shaping means which includes an elongated combined heater and garniture part which embraces the seam and extends for a considerable angle around the tube to each side of the seam. The enlarged arc of the heater enables a relatively heavy pressure to be applied over considerable area and heat is transferred at such area through the relatively heavy paper to shape the tube and to soften and set the thermo-setting adhesive at the corresponding areas to the enclosed filter stubs as well as to seal the longitudinal seam. As a further feature the combined heater and garniture part embodies guide areas of different radii whereby the tube therein is temporarily distorted from the ultimate desired curvature, but when the tube is subsequently free and relaxed it assumes a uniform circular shape.

The apparatus includes a cooler unit through which the tube advances from the heater unit which aids in establishing the desired shape and sets the adhesive while the tube is held confined. The cooler unit includes means for positively circulating cooling fluid in contact with heat radiating surfaces of the cooler bar to increase the efliciency thereof.

r ii Another object of the invention concerns the associa tion of a conveyor belt for the tube and the manner of guiding and directing the belt with relation to the other elements and particularly relative to the heater bar whereby the edges of the belt are deflected just before arriving at the heater area and are not confined under the heater and accordingly the belt is relieved from the deteriorating effects of excessive heating.

The variou features and advantages of the apparatus and the manner of handling the materials and forming the composite continuous tube or rod and the objects of the invention will be made more clear from the detailed description to follow of a representative embodiment of the invention. In connection with the description reference should be had to the accompanying drawings, in which:

FIG. 1 is a view in elevation partially diagrammatic showing the general assembly of a machine for forming the tubes;

FIG. 2 is a view in elevation showing the stub feeding means of FIG. 1 on an enlarged scale and in more detail;

FIGS. 3 and 4 are detail sectional views of the stub transfer means taken on the planes 33 and 44 respectively of FIG. 2;

FlG. 5 is a view in elevation partly broken away of the heater assembly for sealing the longitudinal seam;

FIG. 6 is an end view thereof looking from the right in FIG. 5;

FIG. 7 is a fragmentary top plan view of the left end portion of the unit of FIG. 5;

FIG. 8 is an enlarged cross-sectional view taken on the plane 8-8 of FIG. 5 showing the channel through the heater element for the tube;

FIG. 9 i a front elevational view of the cooler unit assembly for setting the adhesive;

FIG. 10 is a cross-sectional view of the cooler bar and guide taken on the plane 1t}1(i of FIG. 9;

FIG. 11 is a vertical cross-sectional view on an enlarged scale showing the tube guide in the cooler bar with the tube therein;

FIG. 12 is a fragmentary view in elevation of a portion of the cooler bar;

FIG. 13 is an end view of the cooler unit assembly looking from the right in FIG. 12;

FIG. 14 is a front view in elevation of the conveyor belt spreader and underlying tube guide;

FIG. 15 is a bottom plan view of the belt spreader late; P FIGS. 16, 17 and 18 are vertical cross-sectional views taken on the corresponding planes of FIG. 14;

FIG. 19 is a vertical cross-sectional view of the tube and belt at the point of arrival at the heater bar; and

FIG. 20 is a plan view of a section of a completed tube like that assembled and formed in the apparatus of the present invention.

The general arrangement of the machine is shown in FIG. 1 the principal features or elements of which include a main frame 10 upon which is mounted a filter stub feeding means indicated generally at 11 adapted to supply the stubs seriatim to the upper surface of a continuous paper strip S drawn from a supply roll 12 mounted on the frame. Following deposit of filter stubs on the surface of the strip S the strip proceeds through a garniture or tube forming means indicated at 13. At the tube forming means the strip and applied stubs are picked up and carried along by a continuous closed belt conveyor B operating over a horizontal run and down around the drum 14 and driven in any suitable means in timed relation with the feed of the strip. The strip progresses to the left from the tube forming means through .a belt shaper and spreader element 15 to a heater 3 unit indicated generally at 16, then forward through a cooler unit indicated generally at 17 and continues on to a cutting means indicated somewhat diagrammatically at 18 for severing the tube into the desired sections.

The particular details and features or parts of the machine up to the point of the belt spreader are not part of the present invention other than to comprise suitable means for initially feeding the paper strip, depositing the filter stubs thereon in appropriate spaced relation and shaping the paper tube 'around the enclosed serially arranged filter stubs. The strip S may be drawn from the roll 12 by any suitable drive means located in its course of travel. From the roll 12 it proceeds over suitable supporting and guide rollers such as those shown at 25, 26 and 27 to a gum or adhesive applying mechanism indicated generally at 28 designed to .apply the adhesive to the surface of the strip at areas appropriately spaced and separated in accordance with the spacing of the filter stubs. The specific type of gum applying means may vary but as indicated in the present form it includes a gum roller 30 adapated to receive the gum from a suitable supply from which the gum is transferred through roll 31 to a gum die 32, the strip S passing between the die 32 and a backing roll 33. The gummed areas are preferably rectangular in shape and spaced longitudinally of the tube and with their edges spaced fromthe longitudinal edges of the strip. The rolls 32 and 33 are positively driven and connected to be operated in timed relation with the stub depositing means 11 whereby the gummed spots or areas are appropriately located to receive the filter stubs.

A section of the finished tubing is shown in FIG. from which it will be seen that the filter stubs 40 are uniformly spaced along the strip separated by hollow tube sections or blank spaces 41 likewise uniformly spaced and of substantially uniform length longitudinally of the tube. It may be noted at this point that the tube is ultimately cut at appropriate places indicated by the lines 42, 43 into individual tube sections such as indicated at 44 and 45 each comprising a section of the filter material and a recessed end which latter comprises ultimately the open recessed end of a cigarette. The invention is of course applicable to a variety of conditions including differently sized tubes and stubs and kinds and thicknesses of the tube sheet material. A suitable sheet material comprises a sulphite pulp hard calendered bleached kraft paper. It may also be impregnated with desired compounds. In the present case it is also coated on the stub receiving side with a suitable thermo-setting adhesive. In the example described the paper had a thickness of about .006 inch with considerable stiffness as compared with a common limp cigarette paper having a thickness of about .002 inch. The stubs 40 were about 22 to 24 mm. in length and the spaces 41 about 10 to 12 mm. in length.

The areas at which gum is applied by the die 32 are at that point on the lower surface of the strip S, which is also the side pre-coated with a thermo-setting adhesive. The gum or adhesive may be of any suitable type and may be susceptible of setting by heat whereby the filter stubs are securely fixed in position as the tube travels subsequently through the heater unit 16 and the cooler unit 17.

The means for depositing the filter stubs 40 in a row spaced longitudinally upon the upper surface of strip S as it travels from the supporting roll 50 to the left in the machine may be of any suitable type appropriate for the purpose and the details thereof form no part of the present invention. A suitable mechanism for the purpose is shown, however, in FIGS. 2, 3 and 4. It includes three rotary discs 51, 52 and 53 positively driven in timed relation to each other and to the advance of the strip S including the drive for the die rolls 32 and 33. Each disc is provided in its periphery with a groove substantially semicircular in cross section, in which the stubs F (FIG. 1) are adapted to rest. Radial pins or blades projecting through the grooves engage behind the respective stubs and define stub pockets in the groove. A rotary fluted wheel 54 serves to deliver stubs directly to disc 53 from a suitable supply source and radial pins 55 pick up the stubs from the wheel 54. The stubs F are closely spaced along the strip S and in the interest of speed and economy of production it is desirable to provide two or more sources of supply of stubs and accordingly a second supply source includes a fluted wheel 56 like that at 54 adapated to supply stubs to the disc 51 from which they are transferred to disc 52 and from there into alternate pockets of the final disc 53. The patent to Molins 2,748,776 shows one form of stub supply means embodying fluted supply wheels like those indicated in the present drawings at 54 and 56. The stubs from wheel 56 are picked up by radial pins 57 in disc 51 rotating clockwise and carried around to where a finger 58 on stationary plate 59 scoops out the stubs and transfers them to the disc 52 as shown best in FIG. 3. As also there shown the finger 58 is slotted to permit the pins 57 on disc 51 to pass therethrough. A shroud 66 aids in maintaining the stubs in the peripheral groove of disc 51. The stubs are carried around counter clockwise in the peripheral groove of disc 52 by blades 61 to where a finger 62' on stationary plate 63 scoops out the stubs and transfers them to alternate peripheral pockets in disc 53. As shown in FIG. 4 the blades 61 are each provided with a slot to accommodate the finger 62 and permit the blades to deliver up their stub respectively and pass on by. The stationary plate 59 has a groove to receive the outer portion of the stubs and act as a retaining shroud. The wheel 53 therefore is filled with a stub in each pocket behind the respective pins 55 supplied alternately from the wheel 54 and disc 52. The pins 55 are staggered so that only alternate ones pick up a stub from wheel 54.

It is noted that the strip S advances up an incline from the roll 51 to the bottom of the wheel 53 so as to be spaced from the bottom of the respective rolls 51 and 52 but at the roll 53 the filter stubs directly engage with the respective adhesive spots on the strip S and are picked up and carried along on the strip from the roll 53.

. The paper strip S continues on to the left Where it is picked up by the belt B and is drawn along thereby through the garniture or tube forming means 13 where the paper is folded up around the filter stubs. The belt B is comprised of woven fabric but coated with a suitable material to provide a relatively high friction contact with the paper strip S to ensure that the strip is positively advanced. The tube folding means includes a means for applying adhesive to an upwardly projecting lip edge of the strip of appropriate well known character such as by a rotary adhesive applying disc indicated diagrammatically at 65, and the edge is then folded down onto the tube body. The adhesive is preferably of a thermosetting type. The tube folding means may be of any appropriate well known type such as is commonly employed in folding the paper strip around a column of tobacco in making a continuous cigarette rod. Also the patent to Ruau No. 2,145,528 shows a means for forming a tube around filter plugs of a type which may be employed in the present machine. The patent includes an adhesive applying disc such as that indicated diagrammatically in FIG. 1 hereof at 65 for applying adhesive go an upstanding longitudinal edge of the advancing strip Within the tube forming means the belt B is drawn through U-shaped dies including a lower grooved channel plate 66 (FIG. 14) as is common in such devices and accordingly the belt is generally U-shaped in cross section when it begins its travel through belt spreader 15, as indicated at B in FIG. 16. As will be described the heater unit 16 has a guide surface which extends over a large are around the tube. It is desirable, therefore, that the edges of the belt be diverted or spread out into a more horizontal direction by the time it reaches the heater unit so that the edges of the belt advance along the outside of the combined heater and guide bar and the belt is not enclosed within the trough of the heated area. The spreader plate 15 is provided on its lower face with a pair of longitudinal grooves 70 which fan out away from the main semicircular groove 71 for the tube T. The edges of the belt travel in the grooves 70 and are progressively diverted outwardly as indicated in FIGS. l7, l8 and 19. FIG. 19 indicates approximately the position of the belt when it arrives at the heater 16. The surface of the drum 14 is substantially flat which assists in flaring the edges outwardly at the areas of the cooler and heater. The particularly important fact is that the edges of the belt are diverted outwardly so that no part of the belt is enclosed within the heated guide area of the heater unit 16 the detailed construction of which is described below.

The construction of the heater unit 16 is shown in the FIGS. to 8. In general it includes an upper housing part 78 with end plates 79 and 7% the housing being secured to a bracket 81 pivoted upon a rod 82 mounted in brackets 83 fixed to the main frame whereby the heater unit may be swung upwardly .and rearwardly to an ineffective position out of contact with the tube. A handle 85 is provided for that purpose. The unit embodies a longitudinally extending combined heater and guide bar 88 adapted to ride on the upper surface of the formed tube T over and around beyond the seam as will be described shortly. The tube itself rests on the belt B and the tube and is drawn along a bottom longitudinal guide plate 89 underneath the heater having a curved depression to receive the belt and tube. The supporting head and bracket 81 are provided with an adjustable stop means for determining its lowered operative position, such stop means comprising a set screw 90 threaded through a lug 91 on the bracket 81 and provided with a lock nut 92 (FIG. 6). Preferably a stop means such as that described is provided at each of the supporting brackets 83. The heater bar 88 is flexibly suspended from the main housing 78 by a series of spaced supporting ele ments indicated generally at 95. The heater bar may vary as to length dependent upon various factors a length of about 18 inches being illustrative and in such case there preferably are about four supporting elements. Each includes a bolt 96 threaded into the upper part of the heater bar 8%. A spring 97 is interposed between washers 98 and 99 thereon the bottom washer 99 resting on an enlarged annular member 100 seated at the bottom of the opening 101 in the upper housing part 78. Interposed between the heater bar 88 and the housing part 78 are heat insulating layers of material indicated at 102. The rings 100 may also be composed of heat insulating material.

An elongated rod-shaped heating cartridge 105 extends through a bore in the lower part of the heating bar 88 of the electrical resistance type and electrical connections therefor are indicated at 106. The heater bar is maintained at a selected temperature by a thermo-couple 107 attached to the heater bar which controls the electric current to the resistance element through any suitable conventional type means.

As will be apparent from the description thus far, the tube T formed from the strip S is carried along by the belt B underneath the heater, the belt and the superposed tube riding in a generally arc-shaped depression 108 formed in the longitudinally extending base plate 89. Prior to arrival at the heater element 88 adhesive will have been applied to the edge part 110 and that edge folded down into the relation shown in FIG. 8 forming the longitudinal seam.

It should be noted that the total are of the guide area within the heater bar 83 extends for a considerable distance peripherally to each side of the seam area. The

exact extent of the arc may vary dependent upon circumstances but preferably will be in excess of one quarter of the periphery of the tube and usually extends for at least about In the apparatus disclosed herein it extends for about 160 or within about one thirty-second of an inch at each side of enclosing the upper one half of the tube. Heat is applied under pressure to an accordingly large area of the tube causing the heat to penetrate the relatively heavy paper and subject the thermosetting adhesive thereto and cement the tube paper to the stubs and simultaneously seal the seam and shape the tube. As an important feature of the invention it is here pointed out that the bottom curved surface area of the heater bar in which the tube T travels is formed with arcs of different radii, that is the arc portion 111 is on a smaller radius R than the arc portions 112 and 112'which have a radius R about the center of the tube. As indicated in FIG. 8 the area 111 is separated from the areas 112 and 112' by longitudinally extending grooves 113 and 113 respectively. The relation between the radii R and R will vary depending upon various factors. In the present example relating to a cigarette filter tube the radius R was about 0.150 inch corresponding to that of the ultimate finished tube, and the radius R was about 0.125 inch. Accordingly, as indicated in FIG. 8, the center C for the are 111 is about one thirty-second of an inch vertically above the center C for the arcs 112 and 112. The center C coincides substantially with the axis of the tube T and the ultimate filter stubs. In the specific embodiment disclosed in the drawings the distance of the points comprising ends of the are 111 from the center of the circle C is as shown aprpoximately equal to R, but between those two points, beacuse the are 111 is on a smaller radius R, the distance from the point C increases progressively from each end of the arc to the middle of the are where it is quite substantially greater than R being in the range of .010 to .015 of an inch greater which in terms of percentage is about 7% to 10% greater. The efiect of the arrangement just described is to cause the tube area which contacts the arc portion 111 to assume temporarily a shape and radius corresponding thereto which is smaller than the radius of the remaining portion of the tube including the portions in contact with the areas 112 and 112. In other words, heat is applied to the tube including particularly the longitudinal seam area while the latter is in a contracted reduced radius shape. However, by the time the tube reaches the end of the cooler unit in its subsequent progress, it assumes in relaxed condition the desired circular form of substantially uniform radius for the entire periphery. It has been found that if the radius in the heating element is uniform and corresponds to thetube radius the ultimate tube has a flattened shape at the area of the seam due to the character of the material and the necessary operations in effecting the longitudinal seam.

From the heater the tube T progresses through the cooler unit 17 which serves to set the adhesive. It has been found that if the heated tube is not so treated when the sheet material is of the character needed in the present operation and the adhesive is of a character which is desired to be used, the longitudinal seam has a definite tendency to burst open.

The general features of the cooler unit as disclosed in FIGS. 9 to 13 include a housing portion 120 having end plates 121 and 122 attached thereto by any suitable means. The housing 120 is in general U-shaped in crosssection with a closed top and an open bottom in which is mounted the cooler bar 123 coextensive longitudinally with the interior of the housing, the cooler bar in crosssection being shaped substantially as shown in FIGS. 10 and 11. It is secured to the bottomedges of the housing 120 by a series of set screws 124 extending through openings 125 in the cooler bar. The housing 120 is secured to a rear bracket 126 by bolts 127 which bracket is rotatably mounted on a rod 128 secured in a bracket 129 fixed to the frame by bolts 130. The cooler unit is adapted to be swung upwardly and backwardly to an inoperative position on the supporting hinge rod 128 by grasping the handle 135. The forward position and the engagement of the cooling means with the tube T are determined by an adjustable stop and clamp means shown in FIG. 13 comprising a stud 136 screw threaded into the bracket and secured by lock nut 136a. The stud includes an upper end adapted to project into a slot 137 in the pivoted bracket 126 and the stud also has an integral flange 138 on which the bracket 126 rests. A thumb nut 139 is threaded on the upper end of the stud to hold the unit in its operative position. As shown particularly in FIG. 11 the cooler bar 123 has an arcshaped lower face adapted to engage the tube T similarly to the heater bar but in this case the radius of the cooler bar engaging the tube is substantially uniform and corresponds to the radius of the tube T. The tube and belt B are supported underneath by a longitudinally extending plate 140 which may be an extension of the plate 89 provided with a suitable groove to receive the belt and tube.

The cooler bar 123 is cooled by means now to be described. Seated in the notches 141 shown particularly in FIG. are a series of flat plates 142 (FIG. 13) arranged edgewi-se and extending vertically fromthe notches 141 and being of a length substantially equal to the length of the interior of the housing 120. Cooling fluid which may be air is circulated parallel to the fins from a. fan indicated generally at 143, air being directed into the housing between the fins as indicated by the arrows 144 and 145 (FIG. 9), and is discharged from the opposite end of the housing through the dome part 146 having a rear open face permitting the rearward discharge of the air as indicated by the arrow 147 in FIG. 13. i

From the cooler unit the tube continues to the cutter means 18 where it is severed into desired sections which may be for example like the section shown in FIG. 20.

Since various changes in carrying out the above method and in the constructions set forth, which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. In a tube forming machine embodying means for shaping a continuously advanced strip into a tube with a longitudinally extending adhesive seam, and a heater means engaging the seam as the tube advances, a cooler unit through which the tube advances from the heater said unit comprising an elongated bar having a transversely arc-shaped guide surface adapted to engage over and compress the seam as the tube advances, a series of longitudinally extending fins secured to the back of said bar, a housing enclosing said fins, and means for continuously circulating cooling fluid along said fins within said housing.

2. In a tube forming apparatus, means for feeding a continuous strip of web material, means for forming the strip into a tube as it advances including an adhesively engaged longitudinal seam, an elongated heater arranged adjacent the path of the tube having a trough-like guide opening in which the tube advances with transversely curved tube engaging surfaces, the surface area engagengaging the tube at the seam having a radius substantially less than that of the surface areas at each side thereof and less than that of the ultimate tube when expanded into a substantially uniform cylinder.

3. In a tube forming apparatus, means for feeding a continuous strip of web material, means for forming the strip into a tube as it advances including an adhesively engaged longitudinal seam, an elongated guide means including a heater arranged to engage the seam area as the tube advances said guide means having transversely curved surfaces, the surface area engaging the tube at the seam having a radius substantially less than that of the tube and of the surface areas at each side thereof thereby to impress a temporary reduced radius on the tube at the seam area while under heat less than the radius of the tube when expanded into a substantially uniform cylinder.

4. In a tube forming apparatus, means for feeding a continuous strip of web material, means for forming the strip as it advances into a continuous tube including means for applying adhesive to one longitudinal edge portion and folding the two edge portions into superposed relation to form a seam, a generally circular guide means through which the tube advances from the forming means, said guide means including an elongated heater in the direction of tube advance adapted to engage over the seam, the surface area of said guide means at each side of the seam engaging portion having a radius at a transverse section corresponding substantially to that of the ultimate tube when shaped into a uniform cylinder, and the surface at the seam engaging area being of substantially lesser radius.

5. In a tube forming apparatus, means for feeding a continuous strip of web material, means for forming the strip into a tube as it advances including an adhesively engaged longitudinal seam, an elongated tube guide and heater arranged adjacent the path of the tube having a trough-like guide surface in which the tube advances said guide surface having two longitudinally extending channels defining in transverse cross section a middle arc portion between the channels adapted to engage over the seam, and a tube engaging arc portion at each side, the two side are portions having a radius corresponding substantially to that of the ultimate tube when shaped into a cylinder of circular cross section, and said middle are portion having a substantially lesser radius.

6. The method of forming a tube of relatively stifi strip sheet material having in final form a circular cross section comprising advancing the strip and forming it into a tube with an adhesively engaged longitudinal seam,

and applying heat and pressure to the seam area to compress the seam parts together while confining the tube area at the scam in a curved guide of reduced radius less than that of the desired final circular form, said tube thereafter upon cooling expanding into said final form.

7. The method of forming a tube of relatively stifi strip sheet material having in final form a circular cross section comprising advancing the strip and forming it into a tube with an adhesively engaged longitudinal seam, and applying heat and pressure to the seam area to compress the seam parts together while confining the tube area at the seam in a curved guide of reduced radius less than that of the desired final circular form, and thereafter cooling the seam while confining said seam area in a curved guide having a radius corresponding substantially to that of the desired final circular form and therebly setting the seam and effecting the desired permanent s ape.

8. The method of forming a continuous tube from a continuous strip of sheet material with cigarette filter sections longitudinally spaced therein comprising providing one surface of the strip with a coating of thermosetting adhesive, continuously advancing the strip and depositing stub sections of filters in seriatim longitudinally spaced relation on said surface, progressively forming the strip into a tube around said sections including a longitudinal seam, applying heat and pressure progressively along the tube over a considerable peripheral are including the seam to cement the corresponding area to the said sections and simultaneously seal the seam, and progressively cooling the tube along said area directly following the heating while holding the area confined.

9. The method of forming a continuous tube from a continuous strip of relatively stiff paper sheet material with cigarette filter sections longitudinally spaced therein comprising providing one surface of the strip with a coat- 9 ing of thermo-setting adhesive, continuously advancing the strip and depositing stub sections of filters in seratim longitudinally spaced relation on said surface, progressively forming the strip into a tube around said sections including a longitudinal seam, applying heat and pressure progressively along the tube over a considerable peripheral are including the seam While confining the corresponding tube area in a curved guide having a radius at the seam area less than that of the desired ultimate circular form of the tube and less than the radius at each side of the seam area, the heat and pressure serving to cement the heated area to the said sections and simultaneously seal UNITED STATES PATENTS 779,431 Lawless Jan. 10, 1905 1,992,723 Smith Feb. 26, 1935 2,065,561 Boyle et al. Dec. 29, 1936 2,219,491 Podmore Oct. 29, 1940 2,361,052 Patterson Oct. 24, 1944 

